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Triangle - polygon which has 3 sides , 3 angles and 3 vertices

The sum of the measures of the interior angles of any triangle is 180०

Types of triangles:

1) By the lengths of sides:

Equilateral triangle - has three equal sides and three equal angles.

Isosceles triangle - has minimum two equal sides and minimum two equal angles

Scalene triangle - has no equal sides and no equal angles

2) By the measures of angles:

Acute triangle - has all acute angles

Right triangle - has one right angle and two acute angles

Obtuse triangle - has one obtuse angle and two acute angles

The height is the line from the opposite vertex and perpendicular to the base. Every triangle has 3 heights which intersect in one point.

The height can be outside of the triangle. In the obtuse triangle two heights are outside the triangle.

The area of a triangle is always half the product of the height and base

Area = ½ base × height            P△ = ½ a × h

Mikołaj Dobrzyński

- notebook for math :-)